Hetero-interfaces of InP/InGaAs (three monolayers (ML))/InP samples grown by organometallic vapor phase epitaxy (OMVPE) were investigated using X-ray crystal truncation rod (CTR) measurement. The samples were prepared with three different source-gas flow-sequences: (a) conventional sequence, (b) growth interruption, and (c) Ga and In source-gas pulse injection. The results of the X-ray CTR measurement showed that the interfaces between InP cap and InGaAs layers of (b) and (c) were sharper than that of (a) as intended. However, the amount of As in (b) was less than that designed since As atoms desorbed even from the InGaAs layer during the growth interruption. Surprisingly, the Ga atoms distributed wider and peal; compositions of Ga were smaller than those designed for all the samples. It means that the quantum well structures are far from those designed and expected. It suggests that more efforts are necessary to control the distribution of group-m atoms after we solved the problem of group-V atom distributions.